Navigation systems have spread considerably over the last few years. Currently, satellite-assisted navigation systems are utilized very intensively, and have already opened up the home consumer market. For example, the American satellite system GPS (global positioning system) or the Russian GLONASS (global navigation satellite system), which is equivalent to the internationally used umbrella term GNSS (global navigation satellite system), are already being used all over the world. The European system Galileo will also be put to use during the course of the next few years. It is expected that the Galileo system will be fully serviceable in four to five years' time.
The satellite navigation systems predominantly use a frequency range between 1 and 2 GHz. FIG. 9 shows the currently used frequency plan of the so-called lower L-band, the upper L-band and the C-band. In this context, the frequency ranges used are plotted across a frequency axis, which is indicated in units of MHz. The upper part of FIG. 9 represents the lower L-band, wherein all three navigation systems have frequencies associated with them. The individual frequency bands are employed for realizing open services (OS) as well as emergency applications (SOL, safety of life), commercial services (CS) and public services (PRS, public regulated services). In addition, the individual bands have identification codes associated with them, for example in the range from 1,164 MHz to 1,188 MHz, which is associated with the GPS system under the identification code L5, and with the Galileo system under the ID code E5A. In the bottom left area, FIG. 9 further shows the upper L-band, which is also used for navigation systems and is subdivided in a similar manner as the lower L-band. On the right-hand side of the bottom area, FIG. 9 shows the C-band, which is employed in the uplink of the Galileo system and which is within a frequency range of around 5 GHz. This frequency range is used for transmitting information from an earth station to a satellite.
To establish communication within said frequency ranges, antennas may be used which allow correspondingly precise localization of the satellites, and thus of the receiver. For precision applications, which, e.g., have accuracy requirements of less than five meters, attempts have been made to develop antennas which may be operated in all three frequency bands as far as possible. These antennas are currently offered, for example, by the Russian company Javad, www.javad.com, and by North American companies, www.novatel.com and www.sanav.com.
Mostly, antennas are available in one-band versions, such as GPS-L1, or in two-band variations, such as GPS-L1+L2. The current systems have the disadvantage that they are very costly. For example, multi-band systems are only available from a price level above 1,000 euros. Said systems mostly use planar structures on very expensive ceramic substrates, which play a decisive role in the high cost.
In addition, less costly antennas have been conventionally known, which, however, exhibit substantial disadvantages with regard to their levels of accuracy. For example, less costly antenna systems exhibit considerable drawbacks, e.g., with regard to their phase centers and their bandwidths. For example, fluctuations of the phase center in dependence on the angle of incidence are considerable, they comprise several centimeters, for example, and therefore turn out to be far larger than is allowed within the level of accuracy strived for. A further problem manifests itself in the compact design of such systems, which adversely affects their bandwidths and clearly reduces same. Such systems are therefore mostly one-band systems and thus only offer the possibility of receiving one frequency range; for example, only the reception of GPS signals is ensured.